package 牛客.搜狐.跳台阶;

import java.util.Scanner;


public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int i = sc.nextInt();
        System.out.println(function1(i));
    }
    public static int function1(int i){
       int  x = 0;
       int  y = 1;
       int z = 0;
       while(i>0){
           z = y+x;
           x = y;
           y = z;
           i--;
       }
       return  z;
    }
}
